An organic electroluminescent (EL) display, also called an organic light emitting diode (LED) display, generally includes a base substrate, an organic member (e.g., color filter) on the substrate, a gas barrier layer on the organic member, and an organic EL unit on the gas barrier layer.
For example, an organic EL display employing a color filter generally includes a transparent substrate, a color filter layer on the substrate, an overcoat layer on the color filter layer, a gas barrier layer on the overcoat layer, and an organic EL unit that is located on the gas barrier layer and configured to emit white light. The color filter layer and the overcoat layer are made of organic materials.
In such a display, volatile matter (e.g., moisture) volatilizing from the color filter layer or the overcoat layer may cause a dark spot on the organic EL unit and a reduction in luminous efficiency of the organic EL unit. The gas barrier layer blocks the volatile matter so as to prevent the above problems.
For example, JP-A-2007-194168 or US 2006/0017383 corresponding to JP-A-2006-253106 discloses a gas barrier layer formed with a thin film that is represented by the formula AlxTiyOz and formed by an atomic layer deposition method. Typically, such a gas barrier layer has a closely packed structure that improves gas barrier performance.
The AlxTiyOz film is a metal oxide of aluminum (Al) and titanium (Ti). In the formula, the x represents the ratio of atoms of Al, the y represents the ratio of atoms of Ti, and the z represents the ratio of atoms of O. To ensure gas barrier performance, it is required that the AlxTiyOz film be amorphous.
However, depending on the concentration of the Ti of the AlxTiyOz film, a portion of the AlxTiyOz film may change to a crystalline structure that causes a reduction in gas barrier performance. Recently, there has been a strong demand for a gas barrier layer having an improved gas barrier performance for a large-sized display.